Assessment of antimicrobial and antiproliferative activities of a bioactive peptide from the skin secretion of white-lined leaf frog

Abstract

Amphibian skin secretions play a vital role in keeping skin functions working as intended, such as breathing, water and temperature regulation, but mainly in defending against carnivore attack and bacterial infections. The most effective way to prevent microbial resistance is the destruction and permeability of microbial cell membranes, because the component of microbial membrane is evolutionarily steady, so it is less likely to develop drug resistance, especially through mutations. So far, an increasing number of antimicrobial and pharmacological peptides have been successfully isolated and identified from amphibian skin and/or skin secretions. In addition, some of these peptides have been considered as important new drug leads. In this thesis, the cDNA library derived from the lyophilised skin secretion of Phyllomedusa vaillantii was studied by a strategy of molecular cloning and DNA sequencing. Thereafter, a cDNA encoding a peptide precursor was obtained and subject to an NCBI-BLAST search, along with CLUSTAL OMEGA sequence alignment, from which the amino acid sequence of the mature peptide was deduced as: ALWKNMLKGIGKLAGKAALGAVKTLV-NH2. After obtaining the peptide sequence, this peptide was synthesised using solid phase peptide synthesis (SPPS), and the resultant peptide was subject to antimicrobial, antiproliferative and haemolysis tests to ascertain its bioactivities. This peptide was found to exhibit antimicrobial activity against S. aureus, E. coli and C. albicans with MIC values of 2 µM, 2 µM and 64 µM, respectively. Also, this peptide possessed an antiproliferative activity against human lung cancer cell line H838 at 10 µM. However, significant haemolysis activity was observed above peptide concentrations of 16 µM. Taken together, this dermaseptin peptide with potent bacterial effects on both Gram-positive and Gram-negative bacteria further confirmed that frog skin secretion is a rich source for discovery of new bioactive peptides with broad-spectrum antimicrobial activities. This study contributed information to the diversity of peptides, and the MIC and MBC values of QUB-2651 are consistent, indicating that it can be a good antibacterial agent.

Date of Award	Dec 2020
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Xiaoling Chen (Supervisor), Mei Zhou (Supervisor), Lei Wang (Supervisor) & Tianbao Chen (Supervisor)